Mailinglist Archive: opensuse (1126 mails)

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Re: [opensuse] compression tool with high compression ratio, multiple files and fast random access?
  • From: Per Jessen <per@xxxxxxxxxxxx>
  • Date: Wed, 01 Sep 2010 16:10:45 +0200
  • Message-id: <i5lmt5$g0m$1@xxxxxxxxxxxxxxxx>
Per Jessen wrote:

Wilfred van Velzen wrote:


On 2010-09-01 at 09:22, Per Jessen <per@xxxxxxxxxxxx> wrote:
I'm looking for a compression tool (lzma, gzip, zip et al) with
the following characteristics:

1. high compression ratio
2. multiple files per archive
3. very fast decompression/extraction of single files

One of the best from the compression rate point of view is 7z
(well, I know it depends on the type of files you are
compressing). It definitely satisfies 2. No idea about 3, but
worth trying.

Thanks Mark - the last one I tried was indeed 7z (p7zip in the Linux
variation), but it fails miserably on 3. AFAICT, when extracting a
single file, it scans the complete archive.

Try compressing with '-ms=off' option for p7zip and test
decompression speed again...

Interesting, that was a significant improvement. Almost as good as
zip and certainly good enough to make 7za a good candidate. Thanks.

I'm running a lengthy test right now, but my immediate impression is
that 7zip is only marginally slower than zip. Zip typically needs
slightly less than 0.02seconds for an extraction, where as 7zip
typically needs a little more than that. If 7zip does better
compression too (which it should), it's a winner.
However, 7zip for Linux looks a bit, well, unfinished. It doesn't read
filenames from stdin, it doesn't have a --quiet option, and it's still
called 'beta'. Makes me a little wary.



--
Per Jessen, Zürich (17.9°C)

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